Process for the preparation of DOPO-derived compounds and compositions thereof

ABSTRACT

This invention relates to a process for producing compounds derived from 9,10-Dihydro-9-Oxa-10-Phosphaphenantrene-10-oxide (DOPO). In particular, the invention relates to producing DOPO-derived compounds by reacting DOPO with diol compounds in the presence of a catalyst. This invention also relates to DOPO derived composition containing a high melting point diastereomer. The DOPO derived compounds may be useful as flame-retardants.

This application is a continuation of U.S. application Ser. No.14/594,703(now abandoned), filed Jan. 12, 2015, which is a divisional ofU.S. application Ser. No. 13/638,482 (now U.S. Pat. No. 9,012,546),filed on Sep. 28, 2012, which is a national stage entry (371) ofInternational Patent Application No. PCT/US2011/030183, filed Mar. 28,2011, which claims the benefit and priority of U.S. Application No.61/319,580, filed Mar. 31, 2010 and 61/410,694, filed on Nov. 5, 2010.

TECHNICAL FIELD

This invention relates to a process for producing compounds derived from9,10-Dihydro-9-Oxa-10-Phosphaphenantrene-10-oxide (DOPO). In particular,the invention relates to producing DOPO-derived compounds by reactingDOPO with diol compounds in the presence of a catalyst. This inventionalso relates to DOPO derived composition containing a high melting pointdiastereomer. The DOPO derived compounds may be useful asflame-retardants.

BACKGROUND

Phosphorus-containing flame-retardants are perceived to be moreenvironmentally friendly than halogen containing flame-retardants. Inthe field of epoxy resins and laminates, organo-phosphorousflame-retardants with reactive groups, such as those derived from9,10-Dihydro-9-Oxa-10-Phosphaphenantrene-10-oxide (DOPO), are commonlyused in epoxy resin formulations because they react with the epoxy toform a phosphorus-modified epoxy resin. However, “additive”organophosphorus flame-retardants, which do not have reactive groups,are typically not used in epoxy formulations, since it is believed thatcovalent bonding between the epoxy resin and a reactive organophosphorusflame retardant are needed to provide high glass transition temperaturesand dimensional stability.

DOPO-derived additive compounds, useful as flame-retardants, have beenproduced by reacting DOPO with halogen-containing compounds (seeJapanese Kokai Patent Application No. Hei 11[1999]-106619 and JapaneseKokai Patent Application No. P2001-270993A). However, DOPO-derivedcompounds have not heretofore been produced by reacting DOPO with diolcompounds in the presence of a catalyst.

SUMMARY OF THE INVENTION

The present invention relates a process for preparing the compound ofFormula I:

where each R¹, R², R³ and R⁴ are independently hydrogen, C₁-C₁₅ alkyl,C₆-C₁₂ aryl, C₇-C₁₅ aralkyl or C₇-C₁₅ alkaryl; or R¹ and R² or R³ and R⁴taken together can form a saturated or unsaturated cyclic ring, whereinsaid saturated or unsaturated cyclic ring may be optional substituted bya C₁-C₆ alkyl; each m is independently 1, 2, 3 or 4; and n is 2 to about18; comprising reacting a compound of Formula A:

where R³, R⁴ and m are defined above;with a diol compound of Formula B in the presence of a catalyst,optionally a solvent, and optionally an entrainer;HO—(CH₂)_(n)—OH   Formula Bwherein n is defined above.

This invention also relates to a composition comprising the diastereomerof Formula IIa:

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates a process for preparing the compound ofFormula I:

where each R¹, R², R³ and R⁴ are independently hydrogen, C₁-C₁₅ alkyl,C₆-C₁₂ aryl, C₇-C₁₅ aralkyl or C₇-C₁₅ alkaryl; or R¹ and R² or R³ and R⁴taken together can form a saturated or unsaturated cyclic ring, whereinsaid saturated or unsaturated cyclic ring may be optional substituted bya C₁-C₆ alkyl; each m is independently 1, 2, 3 or 4; and n is 2 to about18; comprising reacting a DOPO compound of Formula A:

where R³, R⁴ and m are defined above;with a diol compound of Formula B in the presence of a catalyst,optionally a solvent, and optionally an entrainer;HO—(CH₂)_(n)—OH   Formula Bwherein n is defined above.

The reaction is essentially a dehydration reaction of DOPO tautomerphosphonites with diols, followed by an Arbuzov rearrangement producingthe DOPO dimer derived compound (DiDOPO compound) and water.

One embodiment of the present invention is where n is 2 to 6 and R¹, R²,R³ and R⁴ are all hydrogen.

Another embodiment of the present invention is a process for preparingthe compound of Formula II:

(6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide)

comprising reacting a DOPO compound of Formula C:

with ethylene glycol in the presence of a catalyst, optionally a solventand optionally an entrainer.

One embodiment in the process for making the compounds of Formulas I orII is where the entrainer is present. Another embodiment in the processfor making the compounds of Formulas I or II is where the solvent ispresent. Another embodiment in the process for making the compounds ofFormulas I or II is where both the solvent and the entrainer arepresent.

The molar ratios of diol compound of Formula B or ethylene glycol toDOPO compounds of Formula A or IIA respectively may range from about 0.5to 100, or about 0.5 to 10, or about 0.6 to 5. If the ratio is too low,it leads to insufficient conversion of DOPO. If the ratio is too high,it results in a large recycling of ethylene glycol.

In one embodiment, the diol compound or ethylene glycol with thecatalyst described below is slowly introduced into the DOPO, orDOPO/optional solvent/optional entrainer mixture.

The catalyst that may be used is any suitable catalyst for thedehydration and Arbuzov reactions. General suitable catalysts are alkyhalides, alkali halides, alkaline earth metal halides, transition metalsand their halides or acid catalysts. Arbuzov reaction catalysts areespecially suitable.

Examples of catalysts that may be used include, but are not limited to:sodium iodide, lithium bromide, lithium chloride, potassium iodide,potassium bromide, lithium iodide, C₁-C₆ alkyl iodide, C1-C₆ alkylbromide, 2-iodoethanol, 2-bromoethanol, 2-chloroethanol, 3-iodopropanol,3-bromopropanol, ferric bromide, ferrous chloride, ferrous bromide,manganous halide, copper powder, nickel halide, cobalt chloride, cesiumbromide, palladium chloride, sulfuric acid, aryl sulfonic acid, alkylsulfonic acid, arylalkyl sulfonic acid, hydrochloric acid, hydrobromicacid, hydrofluoric acid, oxalic acid, perchloric acid, trifluoromethanesulfonic acid, fluorosulfonic acid, nitric acid, aluminum chloride,diethyl aluminum chloride, triethylaluminum/hydrogen chloride, ferricchloride, zinc chloride, antimony trichloride, stannic chloride, borontrifluoride, acidic zeolites, acidic clays, polymeric sulfonic acids, ormixtures thereof.

The catalyst may be added in concentrations ranging from about 0.01 wt %to about 10 wt %, or about 0.1 to about 5%, or about 0.1 wt % to about2.5 wt %, based on the total weight of the DOPO compound.

The temperature of the reaction may range from about 100° C. to about250° C., or about 150° C. to 220° C. or about 170° C. to about 210° C.

The reaction may use an optional solvent. The solvent should be chosenso that it will ideally dissolve all or substantially all of the DOPOreactant.

Since the temperature of the reaction will typically be above 100° C.,it is preferable that a high boiling point solvent be used. A highboiling point solvent, is a solvent having a boiling point greater thanabout 150° C. at 1 atmosphere and a melting point greater than about−100° C. Examples of high boiling point solvents, include, but are notlimited to: diphenylmethane, diphenylethane, diphenylpropane, biphenyl,decahydronaphthalene, cyclohexylbenzene, 1,3-diisopropylbenzene,dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethylacetamide(DMAC), ethylene glycol dimethyl ether, ethylene glycol diethyl ether ormixtures thereof.

Lower boiling point solvents may also be used, but in order to get thetemperature high enough, the reaction would be conducted under pressuresuch that the reaction pressure will be equal to or higher than thevapor pressure of the solvent at the reaction temperature. Depending onthe solvent, the reaction pressure for lower boiling point solventswould range from greater than 1 atmosphere to about 10 atmosphere, orgreater than 1 atmosphere to about 5 atmosphere, or greater than 1atmosphere to about 3 atmosphere.

Low boiling point solvents are solvents having a boiling point less thanabout 150° C., or about 100° C. at 1 atmosphere. Examples of low boilingpoint solvents, include, but are not limited to heptane, hexane,petroleum ether, methylcyclohexane; toluene, xylene, mesitylene, ethylbenzene, tetrahydrofuran, 1,4-dioxane, acetonitrile or mixtures thereof.

The amount of solvent in the reaction may range from 0 wt % to about 95wt %, or about 30 wt % to about 85 wt %, or about 60 wt % to about 80 wt%, based on the total weight of the reactant mixture (e.g., reactants,catalysts, solvents and entrainer if present).

Since the reaction generates water, it is advantageously to use anentrainer to remove water in order to push the reaction forward. Anentrainer is an organic solvent that can form azeotropes with water. Theentrainer is usually chemically inert organic liquid whose boilingpoints are below reaction temperature, for example, 150° C., and formazeotropes with water.

In one embodiment, the entrainer is a low boiling point solvent, whereinthe low boiling point solvent has a boiling point lower than about 150°C. at 1 atmosphere.

Examples of entrainers that may be used, include, but are not limited topentane, hexane, heptane, octane, cyclohexane, methylcyclohexane,toluene, xylenes, ethylbenzene, isopropylbenzene or mixtures thereof.

The amount of entrainer required for complete removal of the water canbe determined in manner from the water formation calculated according tothe stoichiometry of the reaction and from the composition of the binaryor ternary azeotrope. It has been found useful to use the entrainer inexcess, advantageously in an amount, which is from 50 to 200% by weightabove the theoretically calculated amount.

The entrainer may or may not be same as the solvent. If the entrainer isdifferent from the solvent, the amount of entrainer may range from about0 wt % to about 30 wt %, or about 1 wt % to about 30 wt %, or about 2 wt% to about 15 wt %, based on the total weight of the reactant mixture(e.g., reactants, catalysts, solvents and entrainer if present).

In a particularly useful embodiment of the process of the invention, theentrainer is added to the reaction mixture before the diol or ethyleneglycol compounds. After a gentle reflux is observed, addition of diol orethylene glycol with catalyst is started. The progress of the reactioncan be followed in a simple manner by collection and separation of theentrainer/water/diol mixture distilled off. The entrainer and diolseparated from the azeotrope can be returned directly, i.e. without anintermediate purification step, to the reaction.

In one embodiment, the process is conducted at the normal pressure andthe entrainer is continuously recycled back to reactor.

The entrainer can also be replaced by vacuum and/or inert gases such asnitrogen, carbon dioxide, and/or helium as long as the water generatedin the process can be removed effectively.

The reaction may be carried out in batch or continuous mode. A series ofreaction vessels with mixers may be used for continuous mode. When incontinuous mode, an excess of diol compound or ethylene glycol is usedand can be recycled back into the process for further reaction.

The reaction time may vary depending on the reaction temperature, typeand amount of catalyst, and the use, type and amount of a solvent and/orentrainer. Typically, the reaction time will be from about 0.5 to about48 hours or about 1 to about 24 hours.

After the reaction, the resulting product of Formulas I or II may bepurified using any conventional method such as washing distillation,filtration and/or drying. In one embodiment, water or water misciblesolvents such as alcohols (e.g., isopropanol), aldehydes or ketones(e.g., acetone) are used to wash the product before and/or afterfiltration.

The peak melting point of the compound of Formula II is preferrablygreater than about 245° C. or about 250° C. For determining peak meltingpoint, a differential scanning calorimeter (DSC) may be used such as a“TA Instruments Q200” analyzer with its standard DSC cell. The DSC isconnected to a PC, which provides user interface and operational systemcontrol. The temperature scale is calibrated at 10° C./min using themelting points of gallium, indium, lead and zinc reference standards.The heat flow scale is calibrated using the heat of fusion of indium.The baseline response is calibrated at 20° C./min with a syntheticsapphire heat capacity standard. All of these calibrations should beperformed according to the instrument manufacturers recommendedprocedures.

The samples are run in gold plated stainless steel crucible at 10°C./min from 0° C. to 400° C. A raw data file containing the sample heatflow and temperature data is saved to the PC hard drive during themeasurement. After the DSC measurement is finished the raw data file isanalyzed for melt behavior. The melting endotherm is integrated toyield, extrapolated onset temperature, peak temperature and heat offusion.

The TA Instrument software is used to determine the peak melting pointby selecting temperature points above and below the peak. If a sampleexhibits multiple peaks, then multiple peak melting points will bereported. The peak melting point is the maximum endotherm for aparticular melting transition. The peak maximum determination is ananalysis used to determine the most remote point, relative to thebaseline, within the chosen limits.

High Melting Point Diastereomer Composition

This invention also relates to a composition comprising the diastereomerof Formula IIa:

It has been discovered that by using the process of the presentinvention, a mixtures of stereoisomers are produced. For the compound ofFormula II, at least three stereoisomers are produced in thecomposition. One is the high melting point diastereomer of Formula IIaand two are lower melting point enantiomers of Formula IIb and IIc.

It is sometimes beneficial to choose a composition with higher amount ofhigh melting point constituents. A composition with a higher “IsomerRatio” of high melting point constituents vs. low melting pointconstituents would be more desirable for high temperature polymerapplications.

In the preset application, the Isomer Ratio may be calculated from DSCcurves as follows:Isomer Ratio=A _(h)/(A _(h) +A ₁),wherein A_(h): area of high melting point peak and A₁: area of lowmelting point peak.Another method of calculating the Isomer Ratio is from ³¹P NMR asfollows:Corrected ratio=(A _(h)-A _(l)×0.5)/(A _(h) +A ₁),wherein A_(h): area of high field peak and A₁: area of low field peak.

The uncorrected ratio=A_(h)/(A_(h)+A₁), wherein A_(h) and A_(l) aredefined above.

It has been found that a corrected ratio obtained from ³¹P NMR is closeto values obtained from DSC curves and therefore a corrected ratio isalways assumed if there is no explicit statement about the Isomer Ratiosobtained from ³¹P NMR.

31P NMR Method:

One NMR spectroscopy procedure that may be used to measure the IsomerRatio is discussed below. This procedure is suitable for thedetermination of Isomer Ratio by weight percent normalization.

Nucleus: 31P; Proton decoupled; Pulse program: zgig30; Collected datapoints (TD): 205 k; Spectral Width (SWH): ˜40322 Hz; Pre-pulse delay(D1): 20 sec minimum (use adequate prepulse delay to ensure all observednuclei have adequate relaxation time); Acquisitions (NS): 16 scansminimum (enough scans to provide good signal to noise); Lock Solvent:CDCl3. Referenced to 85% aqueous phosphoric acid.

The chemical shift of the high melting point isomer appears at the highmagnetic field region around 36.9 ppm and the chemical shift of the lowmelting point isomers appears at the low field region around 37.1 ppm.

It is one embodiment, the composition comprises a plurality of thediastereomer of Formula IIa. In other embodiments, the composition hasan Isomer Ratio of greater than about 0.5, or greater than about 0.6, orgreater than about 0.7, or greater than about 0.8, or greater than about0.9, or greater than about 0.95 or greater than about 0.98, based onusing DSC or 31P NMR Method. For the 31P NMR Method, the Isomer Ratio isthe corrected Isomer Ratio.

Process to Achieve Higher Melting Point Isomers:

In another embodiment, the present invention relates to a method forproducing a higher melting point composition comprising the compound ofFormula II:

comprising contacting a composition containing lower amounts of highmelting point isomers of Formula II, with alcohols, water, or mixturesthereof in the presence of an acid catalyst, thereby producing acomposition containing larger amounts of higher melting point isomers ofFormula II.

Low melting point isomers can be converted to high melting point isomersin the presence of alcohols and/or water at a temperature ranging from 0to 300° C. This isomerization is catalyzed by acid catalysts thatinclude mineral acids and Lewis acids. Mineral acids include sulfuricacid, methanesulfonic acid, hydrochloric acid, phosphoric acid,phosphonic acids and phosphinic acids. Lewis acids are defined as amolecular entity that is an electron pair acceptor and include aluminumchloride, zinc chloride, ferric chloride, etc.

Examples of such acid catalysts include, but are not limited to:sulfuric acid, aryl sulfonic acid, alkyl sulfonic acid, aralkyl sulfonicacid, hydrochloric acid, hydrobromic acid, hydrofluoric acid, oxalicacid, perchloric acid, trifluoromethane sulfonic acid, fluorosulfonicacid, nitric acid, phosphoric acid, phosphonic acids, phosphinic acidsaluminum chloride, diethyl aluminum chloride, triethylaluminum/hydrogenchloride, ferric chloride, zinc chloride, antimony trichloride, stannicchloride, boron trifluoride, acidic zeolites, acidic clays, polymericsulfonic acids, or mixtures thereof

One embodiment to carry out the isomerization is to feed a mixture ofalkylene glycol (e.g., ethylene glycol) and water to the DOPO solutionat a temperature of 25 to 300° C. under elevated pressure or normalpressure. Because the reaction of DOPO+alkylene glycol produces waterin-situ, the mixture of alkylene glycol and water can be replaced bypure alkylene glycol provided that the generated water is not completelyremoved in a timely manner so that it can participate the isomerization.Otherwise, a mixture of alkylene glycol and water is required. Thismixture can be the recovered alkylene glycol and water, which areco-distilled out and condensed during the reaction, or they can beobtained by mixing alkylene glycol with water.

The mixture of alkylene glycol and water can be added at the beginningof the reaction where the conversion of DOPO is essentially zero, duringthe reaction, and/or after the reaction where DOPO is essentiallyconsumed up. If the mixture of alkylene glycol and water is added afterDOPO is consumed up, the mixture can be replaced by water alone,alcohols or their combinations since they do not interfere with thereaction any more except isomerization.

A preferred embodiment of the above process is when the alkylene glycolis ethylene glycol.

The required acid catalysts are preferably those generated in-situduring the reaction; however, external acids can be added to accelerateboth the reaction and isomerization.

A second embodiment includes the treatment of finished compounds ofFormula I or II containing small amount (e.g., <15%) of high meltingpoint isomers by alcohols and/or water in the presence of acid catalystsand in the presence or absence of solvents under elevated pressure ornormal pressure at a temperature range of 25 to 300° C. The treatment isperformed by mixing alcohols, and/or water, acid catalysts, and DiDOPOcontaining small amount (e.g., <15% by weight) of high melting pointisomer(s). This mixture is then heated to a temperature range of 25-300°C. for a length of time until the desired isomer ratio is obtained.Usually the length of time varies from a few minutes to 10 hours,preferably from 0.5 to 8 hours, more preferably from 1 to 5 hours. Theamount of catalyst is from 0.1% to 50% of DiDOPO, preferably from 1 to25%, more preferably from 5 to 15%. The temperature is from 25 to 300°C., preferably from 50 to 250° C., more preferably from 80 to 200° C.This method is particularly advantageous to convert the finished DiDOPOthat is largely composed of low melting point isomers to high meltingpoint DiDOPO.

Use of the Compounds of the Invention

This invention also related to a flame retardant polymer compositioncomprising a polymer and the flame retardant amount of the compounds ofFormula I, II, IIa, IIb, IIc or mixtures thereof.

Polymer that may be used in the flame retardant polymer compositioninclude, but are not limited to: polyolefins, polyesters, polyethers,polyketones, polyamides, polyvinylchlorides, natural and syntheticrubbers, polyurethanes, polystyrenes, poly(meth)acrylates, phenolicresins, polybenzoxazine, polyacetals, polyacrylonitriles,polybutadienes, polystyrenes, polyimides, polyamideimides,polyetherimides, polyphenylsulfides, polyphenylene oxide,polycarbonates, cellulose, cellulose derivatives, cyanate esters,polyphenylene esters, polybutadiene resins, butadiene-styrene resins,butadiene-divinylbenzene-styrene resins, epoxy-modified polybutadieneresins, acrylic or vinyl acetate adhesives, carboxyl-terminatedbutadiene-acrylonitrile copolymers, phenylene ethers, maleicanhydride-grafted butadiene-styrene copolymers, maleicanhydride-modified 4-methyl-1pentene resins, maleated 1-butene-ethylenecopolymers, resins derived from vinylbenzyl ether compounds, epoxyresins or mixtures thereof. Preferably, the polymers are polyolefins,polyesters, phenolic resins, phenol triazine novolaks, cresol triazinenovolaks, triazine phenol epoxy novolaks, triazine cresol epoxynovolaks, polyamides, polyurethanes, polystyrene, epoxy resins ormixtures thereof.

Another embodiment is when the flame retardant composition furthercomprises at least one conventional additive, such as heat stabilizers,light stabilizers, ultra-violet light absorbers, anti-oxidants,anti-static agents, preservatives, adhesion promoters, fillers,pigments, dyes, lubricants, mold releasers, blowing agents, fungicides,plasticizers, processing aids, acid scavengers, dyes, pigments,nucleating agents, wetting agents, dispersing agents, synergists,mineral fillers, reinforcing agents such as glass fiber, glass flake,carbon fiber, or metal fiber; whiskers such as potassium titanate,aluminum borate, or calcium silicate; inorganic fillers and otherfire-retardant additives, smoke suppressants and mixtures thereof.

The other flame retardant additives which may be used with the compoundsof Formulas Formula I, II, IIa, IIb, IIc or mixtures thereof include,but are not limited to, nitrogen-containing synergists such as ammoniumpolyphosphate, melamine, melamine phosphate, melamine cyanurate,melamine pyrophosphate, melamine polyphosphate, phosphate and cyanuratederivatives of guanidine and piperazine, phosphazene compound,polyphophazenes, antimony oxide, silica, talc, hydrotalcite, boratesalts, hydrated alumina such as aluminum hydroxide (ATH), boehmite,bismuth oxide, molybdenum oxide, or mixtures of these compounds withzinc, aluminum and/or magnesium oxide or salts.

The amount of compounds of Formula I, II, IIa, IIb, IIc or mixturesthereof added to the polymer as a flame retardant may be varied over awide range. Usually from about 0.1 to about 100 parts by weight of thecompounds are used per 100 parts by weight of polymer. Preferably about0.5 to about 70 parts of the compounds are used per 100 parts by weightof polymer, or from about 2 to about 50 parts by weight per 100 parts byweight of polymer.

Preferably, the compounds of Formula I, II, IIa, IIb, IIc or mixturesthereof are grounded or milled prior to combining with the polymer. Thed₅₀ particle size after grinding or milling may be less than about 15μm, or less than 10 μm, or less than about 5 μm, or less than about 3 μmor less than about 2 μm. The d₅₀ particle size may even be less than 1μm, such as about 100 nm to 800 nm. A particle size of d₅₀ is the medianparticle size, where half the particles are above the value and half theparticles are below the value. Any suitable milling or grindingtechnique may be used such as jet milling.

To determine median particle size, a Coulter LS-230 counter orequivalent is used with its small volume module. The operatinginstructions of the manufacturer are followed. Alternatively, a Horibalaser light scattering instrument (e.g., Horiba LA900 Model 7991) orequivalent can be used. The procedure involves weighing the sample,typically an amount in the range of about 0.01 gram to about 0.015 gram,into a clean dry aluminum cup that has been washed with deionized waterbefore use. The instrument autosampler disperses a 0.05 g sample inwater using 0.4 ml of 1% Triton X-100 surfactant and ultrasonictreatment. This suspension is circulated through a measuring cell wherethe powder particles scatter a beam of laser light. Detectors in theinstrument measure intensity of the light scattered. The computer in theinstrument calculates mean particle size, average particle size andparticle size distribution from such measurements.

Masterbatches of polymer containing the compounds of Formula I, II, IIa,IIb, IIc or mixtures thereof of this invention, which is blended withadditional amounts of substrate polymer, can contain even higherconcentrations of the compounds e.g., from about 10 to about 1000, orfrom about 25 to about 500, or from about 25 to about 250 parts byweight of the compounds per 100 parts by weight of polymer.

Alternatively, the amount of the phosphorus compounds of Formula I, II,IIa, IIb, IIc or mixtures thereof in the flame retardant polymercomposition is selected so the composition will contain about 0.1 wt %to about 10 wt %, or about 1.0 wt % to about 7 wt %, or about 1.2 wt %to about 5 wt %, or about 1.5 wt % to about 4 wt % phosphorous content,based on the total weight of the composition.

EXAMPLES

The following Examples illustrate the present invention. It is to beunderstood, however, that the invention, as fully described herein andas recited in the Claims, is not intended to be limited by the detailsof the following Examples.

Example 1 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

To a 25 ml 3-necked reaction flask fitted with a Dean-Stark trap,addition funnel, thermocouple, and nitrogen inlet and outlet werecharged 17.082 g DOPO (0.0790 mole), 2.509 g ethylene glycol (0.0404mole) and 0.300 g sodium iodide (0.00200 mole). The reaction mixture washeated to 210° C. and the addition of p-xylene (entrainer) from additionfunnel was started. The water immediately came out with p-xylene andethylene glycol. After the reaction temperature was maintained between190-210° C. for 2 hours, another 1.651 gram of ethylene glycol was addedto compensate those lost. The reaction mixture was kept stirring for onemore hour and then the mixture was diluted with xylene and stirred forhalf hour at 133° C. The slurry was filtered, washed by acetone anddried at 120° C. overnight. A white solid of 14.84 grams was obtainedand the yield was 82%.

Example 2 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

To a 250 ml 3-necked reaction flask fitted with a Dean-Stark trap, twoaddition funnels, thermocouple, and nitrogen inlet and outlet wascharged 80.64 g (0.373 mole) DOPO. The flask was heated and thetemperature was brought to 170° C. The addition of p-xylene from oneaddition funnel was started. After a gentle reflux of xylene inDean-Stark trap was observed, a mixture of 16.682 g (0.269 mole)ethylene glycol with 1.019 g methylsulfonic acid was gradually addedfrom the 2^(nd) addition funnel. The reaction mixture was kept stirringat a temperature range of 170-180° C. for 18 hours, then the reactiontemperature was lowered to 100° C. The obtained slurry was washed by amixture of 140 g water and 11.06 g 50% sodium hydroxide, then filtered,washed by water and dried in an oven. A white solid of 42.125 gcorresponding a yield of 50% was obtained. The uncorrected 31PNMR isomerratio of high melting point isomer/low melting point isomer=0.87. Thecorrected ratio was 0.80.

This example demonstrates that by keeping reaction temperature low sothat water removal was not timely a product with very high content ofhigh melting point isomer was obtained.

Example 3 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

To a 500 ml 4-necked reaction flask equipped with a Dean-Stark trap, amechanical stirrer, two addition funnels, thermocouple, and nitrogeninlet and outlet were charged 87.30 g (0.404 mole) DOPO, 27.4 gp-xylene, and 178 g diphenylpropane. The mixture was brought to atemperature of 200° C. and more p-xylene was added to ensure a gentlereflux in Dean-Stark trap. Addition of a mixture of 43.037 g (0.693mole) ethylene glycol and 0.884 g sodium iodide was then started andcompleted in 5.5 hours. A mixture of aqueous distillate was recycledback to the addition funnel and the addition was completed in 6 hours. Aslurry was observed with good stirrability. A sample was taken and 31PNMR indicated the slurry was composed of 93% DiDOPO and 7% otherphosphorus-containing species. The slurry was mixed with 19 gisopropanol and stirred for half hour at a temperature of 86° C., thenit was filtered, washed by 2×40 g isopropanol, and dried in an oven at atemperature of 130° C. overnight. A white solid of 81.2 g was obtainedwith a purity >99%. The isolated yield was 88%. The uncorrected isomerratio of high melting point isomer/low melting point isomer=0.69. Thecorrected ratio was 0.53.

This example demonstrates that by feeding a mixture of ethylene glycoland water during the reaction a product rich in the high melting pointisomer(s) was obtained.

Example 4 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

To a 250 ml 3-necked reaction flask equipped with a Dean-Stark trap, amagnetic, two addition funnels, thermocouple, and nitrogen inlet andoutlet were charged 46.778 g (0.216 mole) DOPO, 16.50 g p-xylene, and106.70 g diphenylmethane. The mixture was brought to a temperature of200° C. and more p-xylene was added to ensure a gentle reflux inDean-Stark trap. Addition of a mixture of 25.407 g (0.393 mole) ethyleneglycol and 0.639 g sodium iodide was then started and completed in 6hours. A mixture of aqueous distillate was recycled back to the additionfunnel and the addition was completed in 2 hours. A slurry was observedwith very good stirrability. A sample was taken and ³¹P NMR indicatedthe slurry was composed of 93% DiDOPO and 7% other phosphorus-containingspecies.

Example 5 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

Following example 4, but biphenyl was used as a solvent. The slurry ofthe final mixture was composed of 91% DiDOPO and 9% otherphosphorus-containing species.

Example 6 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,3-propanediyl)bis-,6,6′-dioxide

To a 100 ml 3-necked reaction flask equipped with a Dean-Stark trap, amagnetic, two addition funnels, thermocouple, and nitrogen inlet andoutlet were charged 33.004 g (0.153 mole) DOPO and 5.361 g p-xylene. Themixture was brought to a temperature of 200° C. then the addition of amixture of 7.405 g (0.0973 mole) 1,3-propanediol and 0.631 g sodiumiodide was started and completed 1.6 hours. A mixture of aqueousdistillate was recycled back to the addition funnel and the addition wascompleted in 1 hour. Repeat this procedure two times and a sample wastaken. ³¹P NMR indicated the solution was composed of 55% DiDOPO, 30%mono-species and 15% other phosphorus-containing species.

Example 7 High Pressure Process 6H-Dibenz[c,e][1,2]oxaphosphorin,6,6′-(1,2-ethanediyl)bis-, 6,6′-dioxide

To a 100 mL autoclave equipped with a mechanic stirrer, thermocouple,distillation head, and collection vessel were charged 10.80 g DOPO, 3.1g ethylene glycol, 50 g p-xylene (solvent/entrainer) and 0.188 g sodiumiodide. The reaction mixture was first swept by nitrogen flow for 15minutes and then gradually brought to a temperature range of 190-200° C.under 40-41 psig. Liquid started to come out at 194° C. After no moreliquid out, the reaction temperature was slowly raised to 200° C. andthe mixture was easily stirred for 2 hours. After cooling down anddegassing, NMR analysis showed the crude slurry contained 62% DiDOPO,22% DOPO and the rest of being phosphorus-containing species. Another0.78 g of ethylene glycol and 28 g of p-xylene were added into reactorand heated to 190-200° C. After 5 hours, the reaction mixture was cooleddown and diluted with 22 g of p-xylene and 10 g of iso-propanol. NMRanalysis indicated 90% DiDOPO.

Example 8 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide with a relatively low Isomer Ratio

To a 500 ml 4-necked reaction flask equipped with a Dean-Stark trap, amechanical stirrer, two addition funnels, thermocouple, and nitrogeninlet and outlet were charged 88.36 g (0.409 mole) DOPO, 43.60 gp-xylene, and 177 g diphenylmethane. The mixture was brought to atemperature of 200° C. to obtain a gentle reflux in Dean-Stark trap.Addition of a mixture of 61.84 g (0.996 mole) ethylene glycol and 0.925g sodium iodide was then started and completed in 14.5 hours. A samplewas taken and ³¹P NMR indicated the slurry was composed of 82% DiDOPO,9% phosphonic acid and other phosphorous-containing species. Theuncorrected ratio of high melting point isomer(s)/total isomers=0.41.The corrected ratio is 0.12. This example demonstrates that by feedingethylene glycol free of water a product rich in the low melting pointisomers was obtained. A summary of some of the Examples is shown belowin Table 1.

TABLE 1 SUMMARY OF EXAMPLES Example 1 2 3 4 5 7 8 Charge DOPO/ EG/cat.EG/cat. EG/cat. EG/cat. DOPO/EG/ EG/cat. mode EG added added added addedcatalyst added catalyst contin- contin- contin- contin- Charged contin-Charged uously uously uously uously once, closed uously once and and andsystem without recycled recycled recycled recycle Catalyst NaI Methyl-NaI NaI NaI NaI NaI sulfonic acid Temp (° C.) 190-210 170-175 190-200190-200 190-200 190-200 190-200 Entrainer p-xylene p-xylene p-xylenep-xylene p-xylene xylene xylene Solvent No No Dipheny- Diphenyl-Biphenyl xylene Diphenyl- propane methane methane CrudeYield 93% 91% 92%90% 82% Isolated 82% 50% 88% 83% yield Stirrability Difficult Kind ofEasy Very Easy Very Easy Good Easy difficult Ratio by 0.51 0.87 0.690.62 0.58 0.57 0.41 ³¹P NMR Ratio by 0.26 0.80 0.53 0.43 0.37 0.36 0.12³¹P NMR- corrected Ratio by 0.82 0.61 DSC Corrected ratio = (area of lowfield peak − 0.5* area of high field peak)/(area of low field peak +area of high field peak)

Example 9 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

To a 500 ml 3-necked reaction flask fitted with a Dean-Stark trap, anaddition funnel, thermocouple, and nitrogen inlet and outlet was charged89.0 g (0.412 mole) DOPO, 40.9 g p-xylene, 182.8 g diphenylmethane. Themixture was heated and the temperature was brought to 200° C. After agentle reflux of xylene in Dean-Stark trap was observed, a mixture of61.895 g ethylene glycol with 0.918 g sodium iodide was gradually addedfrom the addition funnel. The reaction mixture was kept stirring at atemperature range of 190-200° C. After about 16 hours, the mixture ofEG/NaI was used up and a recovered 48 mL EG/H2O from distillate was fedcontinuously at a temperature range of 200-25° C. and completed in 4hours. Then the mixture was then heated back to 190° C. to removeethylene glycol and water in ˜1 hour. After cooled down, the reactionmixture was subjected to filtration and isopropanol washes, and thendried at 130° C. Samples were taken during the reaction and the isomerratios were measured by ³¹P NMR. Since the reaction generatedby-products, the isomer ratios were normalized. The results are shown inTable 2.

TABLE 2 HIGH MELTING POINT (MP) ISOMER CONTENT VS. TIME OF REACTION INEXAMPLE 9 Phos- DOPO High Mp High MP EG/NaI EG/H₂O phonic conver- IsomerIsomer Time remaining added acid sion (% un- (%, (hrs) (ml) (ml) (mole%) (%) corrected) corrected) 13.5 6  9 93 44 17 14.6 2 11 98 49 24 16.10  0 11 100  52 28 17.1  5 11 52 28 18.1 12 11 61 41 20.6 25 11 60 4021.6 48 11 88 82

This example demonstrates that high melting point isomer(s) can beobtained by converting low melting point isomer by ethylene glycol andwater in the presence of acid catalysts.

Example 10 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide

A 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide composition (7.866 g) containing 88% low melting pointisomer was mixed with 85% aqueous phosphoric acid (0.189 g) anddiphenylpropane (42 g). The mixture was gradually heated to 200° C. andwas kept at this temperature for 2.5 hours. Samples were taken duringthe treatment and measured by 31P NMR. The results were shown in Table 3below:

TABLE 3 ISOMER CONTENT VS. REACTION TIME FOR EXAMPLE 10 Time (hrs) LowMp Isomers % High mp Isomer % 0 88 12 1 81 19 2.5 48 52

This example demonstrates that treating6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide rich in low melting point isomers by aqueous acid catalystat high temperature increased content of high melting point isomer.

Example 11 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,3-propanediyl)bis-,6,6′-dioxide

6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide composition (57.9 g isomer ratio=0.43, low meltisomer=0.57) was mixed with 134.5 g diphenylmethane, and 3.1 g 85%phosphoric acid in a flask equipped with additional funnel, Dean-Starktrap, mechanic stirrer, and thermocouple. The mixture was heated to 150°C. Water (13 g) was slowly added to the reaction mixture andcontinuously distilled out. After 12 ml water was collected, thereaction was set to the total reflux and the reaction mixture wasstirred for 2.5 hours at this temperature. Then the reaction temperaturewas lowered to 126° C. and isopropanol (70.4 g) isopropanol was added.The mixture was subsequently cooled, filtered, washed by 82 gisopropanol and dried at 130° C. in an oven overnight. A sample wastaken and ³¹P NMR result showed an isomer ratio of 0.90 (low meltisomer=0.10).

This example demonstrates that treating6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,2-ethanediyl)bis-,6,6′-dioxide rich in low melting point isomers by water in the presenceof an acid catalyst increased the content of high melting point isomer.

Example 12 6H-Dibenz[c,e][1,2]oxaphosphorin, 6,6′-(1,3-propanediyl)bis-,6,6′-dioxide

To a 1 L reaction flask equipped with mechanic stirrer, thermometer,pressure gauge, and Dean-Stark trap were charged with 100.00 g DOPO,0.10 g sodium iodide, 0.28 g ethylene glycol, and 400 g mixed xylenes.The reaction mixture was heated to 200° C. under about 40 psig. Asolution of 0.90 g sodium iodide in 50.00 g ethylene glycol wasgradually fed to the mixture in a course of 14 hours. Subsequently themixture was kept to stir at 198-200° C. for 6 hours. A slurry sample wasthen taken. ³¹P NMR showed that DOPO was essentially consumed with aproduct isomer ratio=0.43 and the presence of phosphonic acid (about 3mole % of DOPO). In order to increase the isomer ratio, water (120 g)was slowly fed to the reaction mixture at 173° C. in a course of 5hours. At the end of the water treatment, a sample was taken and ³¹P NMRshowed a product isomer ratio=0.94.

This example demonstrates that high melting point isomer(s) can beobtained by converting low melting point isomer by water.

Example 13 Use of 6H-Dibenz[c,e][1,2]oxaphosphorin,6,6′(1,2-butanediyl)bis-, 6,6′-dioxide as a flame retardant in epoxylaminate

High purity DOPO was loaded into a reactor and a given amount of mixedxylenes was then pumped into the reactor. A 2.62 wt % NaI/EG solutionwas prepared and charged to the reactor. The contents were then agitatedand heated to 198° C. in 5-6 hours while the pressure was maintained at40-41 psig. Once the contents reached the reaction temperature, aco-feed containing the 2.62 wt % NaI/EG and mixed xylenes was started.The co-feed lasted a minimum of about 14 hours.

The xylene feed rate was on the order of 1 lb/min. After an 11.5-hourfeed and 2-hour hold, the reactor became full. It was cooled to 190° C.,and a sample of the reactor slurry was collected. NMR results indicatedthat the DOPO conversion was about 72% at this point. The reactor wasre-heated to 197-199° C., and the co-feed was conducted for another 5hours, followed with 2.5 hour hold. The DOPO conversion was then about93% at the end of the second co-feed. The reaction mixture was quenchedwith IPA and cooled slowly to −100° C.

Once cooled, the contents of the reactor were filtered and the wetcakewas then washed three times with fresh IPA and vacuum dried at 130° C.

Approximately 100 g of the sample prepared above was added to a 2 LErlenmeyer flask, along with 2.0 kg of chloroform and 0.4 kg of2-propanol. The mixture was stirred for about 15 minutes at 65° C. Themixture was removed from heat and allowed to cool slowly withoutstirring to room temperature. The erlenmeyer was then placed in an icebath for about 1 hour. The white solid was vacuum filtered through amedium glass fritted funnel, rinsed with about 100 mL of 2-propanol anddried at 170° C. for 5 h. Three batches of the resultant dried powderwere combined and jet-milled to smaller particle size having a d50 ofabout 2 to 4 μm to afford 130 g of a very high purity6H-Dibenz[c,e][1,2]oxaphosphorin, butanediyl)bis-, 6,6′-dioxide flameretardant sample. The isomer ratio of the sample was about 0.98.

In general, stock solutions of advanced resin, curative and promoter areall prepared and stored separately to facilitate experimentation. A 50wt % o-cresolphenol epoxy novolac resin solution, NPCN®-703 (Nan YaPlastics Corporation), containing 50 wt % 2-butanone (MEK) was prepared.Durite SD-1702 novolac curing agent was obtained from HexionCorporation. A novolac resin solution was prepared by dissolving 50 wt %SD-1702 in 50 wt % MEK solvent.

A flame retardant resin mixture containing 3.0 wt % P was prepared byblending 128.8 g of 50 wt % NPCN 703 solution, 62.7 g of 50 wt % SD-1702solution, 14.0 g of the flame retardant, 14.0 g of melaminepolyphosphate Melapur 200 (M-200) from BASF Corporation and 0.070 g2-phenylimidazole promoter. An additional 11 g MEK was added to themixture. The novolac to promoter ratio was about 448. The flameretardant was insoluble in the resin solution until making contact withthe hot gel plate, where it dissolved completely at high temperature.About 0.5-1 mL of the resin mixture was added to a hot cure plate(Thermo-electric company) at about 170-172° C. A tongue depressor wassplit in half lengthwise, and half of the depressor was used to move theresin on the hot plate until stiffness was noted and then lifting theresin with the flat part of the depressor until string formation ceased.The gel time was 3 minutes, 16 seconds, determined by the point whereresin “strings” could no longer be pulled from the resin mixture and theepoxy became “tack free”. The resin mixture was mixed thoroughly using ahigh shear mixer stirred at 6,000 rpm for about 15 minutes.

An 11 inch by 11 inch square woven glass fabric (7628 glass with 643finish from BGF Industries) was cut to size from a large roll andstapled to wood supports (12 inches long, 1 inch wide and 1/16 inchthick) on the top and bottom ends of the fabric. The wood supportscontained holes in the corners for inserting paper clips on one end forhanging the fabric in the B-stage oven. The A-stage, or resin varnish,was painted on the front and back of the fabric. Paper clips wereunfolded and inserted into the both holes of one wood support. Theresin-saturated fabric was hung from aluminum supports in a laboratoryfume hood and allowed to drip dry for about one minute before hanging ina pre-heated (to 170° C.) forced air Blue M oven (Lab Safety SupplyInc., a unit of General Signal) for 1 minute, 20 seconds. The edges ofthe B-staged prepreg were removed by reducing the sheet dimensions to 10inch by 10 inch. The sheet was cut into four 5 inch by 5 inch sheets andweighed before stacking the four layers of prepreg between two layers ofPacothane release film (Insulectro Corp.) and two steel plates (⅛ inchthick, 12 inch by 12 inch square dimensions). The laminate was formed inthe hot press at 5,000 psig for 1 hour. The resulting laminate was 0.03inches thick, contained 45.5 wt % resin and underwent 17 wt % resinoverflow during pressing. Five 0.5 inch wide coupons were cut from thelaminate using a diamond saw, and the coupon edges were smoothed withsandpaper. The flammability of the coupons were screened by ASTMD3801-06 using an Atlas UL-94 burn chamber, resulting in a V-0 ratingwith 29 seconds total burn time for the two ignitions on all fivecoupons. No single burn was greater than 10 seconds.

The glass transition temperature of the laminate was about 185° C. andthe TGA was about 322° C. for a 1% loss, about 342° C. for a 2% loss andabout 363° C. for a 5% loss.

Components referred to by chemical name or formula anywhere in thespecification or Claims hereof, whether referred to in the singular orplural, are identified as they exist prior to coming into contact withanother substance referred to by chemical name or chemical type (e.g.,another component, a solvent, or etc.). It matters not what chemicalchanges, transformations and/or reactions, if any, take place in theresulting mixture or solution as such changes, transformations, and/orreactions are the natural result of bringing the specified componentstogether under the conditions called for pursuant to this disclosure.Thus the components are identified as ingredients to be brought togetherin connection with performing a desired operation or in forming adesired composition. Also, even though the Claims hereinafter may referto substances, components and/or ingredients in the present tense(“comprises”, “is”, etc.), the reference is to the substance, componentor ingredient as it existed at the time just before it was firstcontacted, blended or mixed with one or more other substances,components and/or ingredients in accordance with the present disclosure.The fact that a substance, component or ingredient may have lost itsoriginal identity through a chemical reaction or transformation duringthe course of contacting, blending or mixing operations, if conducted inaccordance with this disclosure and with ordinary skill of a chemist, isthus of no practical concern.

The invention described and claimed herein is not to be limited in scopeby the specific examples and embodiments herein disclosed, since theseexamples and embodiments are intended as illustrations of severalaspects of the invention. Any equivalent embodiments are intended to bewithin the scope of this invention. Indeed, various modifications of theinvention in addition to those shown and described herein will becomeapparent to those skilled in the art from the foregoing description.Such modifications are also intended to fall within the scope of theappended Claims.

The invention claimed is:
 1. A process for preparing a compound ofFormula I:

wherein each R¹, R², R³ and R⁴ are independently hydrogen, C₁-C₁₅ alkyl,C₆-C₁₂ aryl, C₇-C₁₅ aralkyl or C₇-C₁₅ alkaryl; or R¹ and R² or R³ and R⁴taken together form a saturated or unsaturated cyclic ring, wherein saidsaturated or unsaturated cyclic ring is optionally substituted by aC₁-C₆ alkyl; each m is independently 1, 2, 3 or 4; and n is 2 to about18; comprising reacting a compound of Formula A with a diol compound ofFormula B in the presence of a catalyst, optionally a solvent, andoptionally an entrainer:

wherein R³, R⁴ and m are defined above;HO—(CH₂)_(n)—OH   Formula B wherein n is defined above.
 2. The processof claim 1, wherein n is 2 to 6 and R¹, R², R³ and R⁴ are hydrogen. 3.The process of claim 1, wherein both the solvent and the entrainer arepresent.
 4. The process of claim 1, wherein said catalyst is an alkylhalide, an alkali halide, an alkaline earth metal halide, a transitionmetal, a transition metal halide, or an acid catalyst.
 5. The process ofclaim 1, wherein the reaction takes place at a temperature ranging fromabout 100° C. to about 250° C.
 6. The process of claim 1, wherein thereaction takes place in a reactor, the reaction produces water, andwherein the water and the diol compound of Formula B are continuouslyrecycled back to the reactor.
 7. The process of claim 1, wherein thecatalyst is an acid catalyst.
 8. The process of claim 7, wherein saidacid catalyst is sulfuric acid, aryl sulfonic acid, alkyl sulfonic acid,aralkyl sulfonic acid, hydrochloric acid, hydrobromic acid, hydrofluoricacid, oxalic acid, perchloric acid, trifluoromethane sulfonic acid,fluorosulfonic acid, nitric acid, aluminum chloride, diethyl aluminumchloride, triethylaluminum/hydrogen chloride, ferric chloride, zincchloride, antimony trichloride, stannic chloride, boron trifluoride,acidic zeolites, acidic clays, polymeric sulfonic acids, or mixturesthereof.
 9. A process for preparing a compound of Formula II:

comprising reacting a compound of Formula C with ethylene glycol in thepresence of a catalyst, optionally a solvent, and optionally anentrainer:


10. A method of increasing a content of high melting point isomers in amixture of stereoisomers comprising contacting a composition containinginitial amounts of high melting point diastereomers of Formula IIa, andinitial amounts of low melting point enantiomers of Formulas IIb andIIc:

with alcohols, water, or mixtures thereof, in the presence of an acidcatalyst to convert at least a portion of the low melting pointenantiomers of Formulas IIb and IIc to high melting point diastereomersof Formula IIa.
 11. The method of claim 10, wherein said acid catalystis sulfuric acid, aryl sulfonic acid, alkyl sulfonic acid, aralkylsulfonic acid, hydrochloric acid, hydrobromic acid, hydrofluoric acid,oxalic acid, perchloric acid, trifluoromethane sulfonic acid,fluorosulfonic acid, nitric acid, phosphoric acid, phosphonic acids,phosphinic acids, aluminum chloride, diethyl aluminum chloride,triethylaluminum/hydrogen chloride, ferric chloride, zinc chloride,antimony trichloride, stannic chloride, boron trifluoride, acidiczeolites, acidic clays, polymeric sulfonic acids, or mixtures thereof.